Most commercial optical mounts suffer from a variety of problems when trying to use them outside of a laboratory environment. One major problem is that the commercial optical mounts tend to drift in angle over relatively small temperature variations. Secondly, they also suffer from “lock-and-walk”, meaning that once the optical mount is aligned and adjusted properly, it then needs to be locked into place, and the act of locking it actually induces forces that cause the mount to move from its aligned position. For relatively small optics, such as those used in laser systems, these common problems have been addressed by using precision, customized, flexure-based optical mounts. For larger optics, such as those used in imaging systems, the dimensional scaling of existing mount designs results in bulky and massive devices. Precision mounting of large optical elements, which are intended to be used over wide temperature ranges and/or vibration profiles, is often a challenging engineering effort.
Conventional optical element mounts are generally not suitable to stably position optical elements which will be used in rugged temperature and vibration environments, especially as the optical elements increase in size. Typically, conventional adjustable optical element mounts are suspended from a base support structure by a system of screw jacks and springs.
In conventional optical mounts, an optical element is normally affixed to a plate that is suspended from, and movable with respect to, a backup support plate that is firmly mounted to an optical bench. In a free-space laser system, for example, as the laser beams are generally directed substantially horizontal, the optical element's surface normals are typically positioned to be perpendicular to gravitational forces. Thus, the optical elements are cantilevered from the surface of a support backup plate which must rigidly support the weight of the optical element suspended therefrom. The use of these commercially-available optical mount designs is common practice for laboratory-based optical systems. However, because of the cantilevered design, and lack of locking features, optical mounts of this design prove completely unsuitable as the size of the optical element increases and/or the environmental conditions worsen.
Further, in conventional optical mounts, the tip and tilt adjustment are separately operated by different mechanisms. However, both adjustment mechanisms operate on the same optical element support plate in such a way that leads to a common problem known as “crosstalk”, in which the adjustment of one axis results in a small amount of unintended motion in the other independent orthogonal axis.
In other conventional mounts, a series of springs between the rigid support plate and the moveable plate upon which the optical element (e.g. a mirror) is mounted, provides a force that maintains one or more optical mount actuators in compression or tension, thereby stabilizing the optical element. However, conventional type spiral springs have little or no resistance to shear forces, which are unsuitable for supporting heavy optical elements cantilevered from the rigid mount. Therefore, pins or ball type sockets are generally required to support the moveable plate. These supporting devices introduce frictional hysteresis and crosstalk which inherently reduces the required position accuracy and stability of the optical elements.
Further, where screw type actuation is manually or mechanically manipulated to position the optical elements, some type of locking mechanism is frequently desired. During activation of the locking mechanism, positioning errors may be introduced. For example, the simple procedure of tightening a setscrew to lock an optical element usually requires tedious and time-consuming trial-and-error to align the one or more mirrors to a desired setting.
Additionally, for example in a laser system, the efficiency of a laser is critically dependent on the angular alignment of the optical components defining the laser resonator. Mechanical vibrations and ambient temperature changes transmitted to the optical mount assemblies jeopardize the mirror alignment of the laser system and negatively affect overall system performance.
A need, therefore, exists for an improved apparatus that overcomes the above referenced drawbacks.